The present invention generally relates to novel antitumor agents and pharmaceutically acceptable acceptable salts thereof, processes for the manufacture of these novel compounds and medicaments, containing them. The compounds of the invention have antiproliferative and differentiation-inducing activity, which results in inhibition of tumor cell proliferation, induction of apoptosis and inhibition of invasion. The invention concerns thus also the use of such compounds for the treatment of diseases such as cancer and for the manufacture of corresponding medicaments.
Cancer is one of the major causes of death. Cancer exceeds heart and cerebrovascular diseases in causing death. Accordingly, many studies have been conducted with enormous expense and time to overcome cancer. However, despite a variety of therapies such as surgical operation, radiation therapy and chemotherapy, there is still a great need for improved anticancer therapeutics. Among these therapies, chemotherapy is one of the main areas for cancer treatment. Most drugs show their effect by inhibiting DNA from expressing their cytotoxicity and as a result, injuring tumor cells. However, chemotherapy lacks selectivity and consequently, does not sufficiently differentiate between tumor cells and normal cells, and therefore, adverse reactions expressed in normal cells have limited their use in therapy. Up to now, no satisfactory drugs are believed to have been discovered, and thus, an anticancer drug with reduced toxicity, better tolerability and a high therapeutic effect is very much desired.
Transcriptional regulation is a major event in cell differentiation, proliferation, and apoptosis. Transcriptional activation of a set of genes determines cell destination and for this reason transcription is tightly regulated by a variety of factors. One of its regulatory mechanisms involved in the process is an alteration in the tertiary structure of DNA, which affects transcription by modulating the accessibility of transcription factors to their target DNA segments. Nucleosomal integrity is regulated by the acetylation status of the core histones. In a hypoacetylated state, nucleosomes are tightly compacted and thus are nonpermissive for transcription. On the other hand, nucleosomes are relaxed by acetylation of the core histones, with the result being permissiveness to transcription. The acetylation status of the histones is governed by the balance of the activities of histone acetyl transferase (HAT) and histone deacetylase (HDAC). Recently, HDAC inhibitors have been found to arrest growth and induce apoptosis in several types of cancer cells, including colon cancer cells, T-cell lymphoma cells, and erythroleukemic cells. Given that apoptosis is a crucial factor for cancer progression, HDAC inhibitors are promising reagents for cancer therapy as effective inducers of apoptosis (Koyama, Y., et al., Blood 96 (2000) 1490–1495).
EP-A 0 847 992 describes monoacylated o-phenylendiamine derivatives as cell differentiation inducers. The same type of compounds is also the subject of EP-A 0 242 851. The compounds described in these applications are almost exclusively o-phenylene derivatives monoacylated with derivatives of benzoic acid.
Monoacylated o-phenylendiamines are known in the art as precursors for the preparation of the corresponding benzimidazoles, such preparation methods are e.g. described in DE-A 2 062 265; FR 2 167 954; Rastogi, R., and Sharma, S., Indian J. Chem., Sect. B, 21B (5) (1982) 485–487; Moll, R., et al., Z. Chem. 17 (1977) 133–134; and Hassan H., et al., Indian J. Chem. 39B (2000) 764–768.
As can be seen, there exists a need to provide compounds with improved properties such as increased tolerability, less toxicity and less side effects.